1. Field of the Invention
This invention relates to containers, and more particularly, to reinforced bulk material containers for storing and shipping fluid materials.
2. Prior Art
Containers for storing and shipping bulk quantities of materials are known in the prior art. These prior art containers include metal drums, plywood bins, metal frame constructions and fiberboard or cardboard boxes and drums. Containers for the bulk storage and shipment of fluid materials, in particular, commonly consist of metal drums because of their strength and durability. However, since these types of containers are relatively costly to produce, they are typically saved and reused, which is also at a relatively high cost, particularly in relation to the storage and shipment of the empty containers.
Although fiberboard and cardboard boxes and drums are generally less expensive to make, and some of them therefore may be economically disposed of after a single use, they may have less strength and durability than metal or plastic drums and similar "hard" containers. For instance, cardboard containers may not have sufficient "stacking" strength, and when the container is used for holding fluid material, there is a tendency for the container walls to bulge outwardly under the pressure of the contents. Accordingly, they are not used as often as otherwise may be desired in the storage and shipment of bulk materials, and especially fluid materials.
Efforts have been made in the prior art to develop stronger and more durable fiberboard and cardboard containers for the bulk storage and shipment of materials, including fluid materials. Examples of some prior art constructions are shown in U.S. Pat. Nos. 2,603,402, 3,294,306, 4,105,153, 4,341,338 and 4,623,075. U.S. Pat. Nos. 2,603,402 and 3,294,306, in particular, disclose cardboard containers having structure to improve stacking strength and/or bulge resistance. Note the rolled flanges at the top and bottom of the container in U.S. Pat. No. 2,603,402, and the interengaged flanges and corner posts in U.S. Pat. No. 3,294,306. The rolled flanges in the '402 patent have cuts that define mitered corners which frictionally interengage when the flanges are in their erected condition, and the flanges in the '306 patent have cuts which define openings that receive the corner posts when the container is in its erected condition. The mitered corners in the '402 patent do not interlock, but merely frictionally engage one another to retain them in their rolled condition, and there is no provision for receiving corner posts to improve stackability. The flat flanges in the '306 patent do appear to interlock with the corner posts inserted in the openings at the corners of the box, to retain the flanges and corner posts in position, but there does not appear to be any interlocking of the flanges in the absence of the corner posts, and the flat flanges would appear to provide only limited bulge resistance.
Accordingly, there exists a need for an economical bulk material container of cardboard or fiberboard construction having rolled flanges at least at one end of the container to resist bulging of the sidewalls, and corner posts to improve stackability, wherein the bulge resisting flanges have interlocking portions to retain them in position in either the presence or the absence of the corner posts.